Why is the sky pink?


On Mars, the sky is pink during the day, shading to blue at sunset. What planet did you think I was talking about?

On Earth, the sky is blue during daytime, turning red at as the sun sinks toward night.

Scattering light

Well, it’s not quite as simple as that: if you ignore your dear sainted mother’s warning and look at the Sun, you’ll see that the sky immediately around the Sun is white, and the sky right at the horizon (if you live in a place where you can get an unobstructed view) is much paler. In between the Sun and the horizon, the sky gradually changes hue, as well as varying through the day. That’s a good clue to help us answer the question every child has asked: why is the sky blue? Or as a Martian child might ask: why is the sky pink?

First of all, light isn’t being absorbed. If you wear a blue shirt, that means the dye in the cotton (or whatever it’s made of) absorbs other colors in light, so only blue is reflected back to your eye. That’s not what’s happening in the air! Instead, light is being bounced off air molecules, a process known as scattering. Air on Earth is about 80% nitrogen, with almost all of the rest being oxygen, so those are the main molecules for us to think about.

As I discussed in my earlier article on fluorescent lights, atoms and molecules can only absorb light of certain colors, based on the laws of quantum mechanics. While oxygen and nitrogen do absorb some of the colors in sunlight, they turn right around and re-emit that light. (I’m oversimplifying slightly, but the main thing is that photons aren’t lost to the world!) However, other colors don’t just pass through atoms as though they aren’t there: they can still interact, and the way we determine how that happens is again the color.

The color of light is determined by its wavelength: how far a wave travels before it repeats itself. Wavelength is also connected to energy: short wavelengths (blue and violet light) have high energy, while long wavelengths (red light) have lower energy. When a photon (a particle of light) hits a nitrogen or oxygen molecule, it might hit one of the electrons inside the molecule. Unless the wavelength is exactly right, the photon doesn’t get absorbed and the electron doesn’t move, so all the photon can do is bounce off, like a pool ball off the rail on a billiards table. Low-energy red photons don’t change direction much after bouncing–they hit the electron too gently for that. Higher-energy blue and violet photons, on the other hand, scatter by quite a bit: they end up moving in a very different direction after hitting an electron than they moving before. This whole process is known technically as Rayleigh scattering, for the physicist John Strutt, Lord Rayleigh.

The blue color of the sky

Not every photon will hit a molecule as it passes through the atmosphere, and light from the Sun contains all the colors mixed together into white light. That means if you look directly at the Sun or the sky right around the Sun during broad daylight, what you see is mostly unscattered light, the photons that pass through the air unmolested, making both Sun and sky look white. (By the way, your body is pretty good at making sure you won’t damage your vision: your reflexes will usually twitch your eyes away before any injury happens. I still don’t recommend looking at the Sun directly for any length of time, especially with sunglasses, which can fool your reflexes into thinking everything is safer than it really is.) In other parts of the sky away from the Sun, scattering is going to be more significant.

The Sun is a long way away, so unlike a light bulb in a house, the light we get from it comes in parallel beams. If you look at a part of the sky away from the Sun, in other words, you’re seeing scattered light! Red light doesn’t get scattered much, so not much of that comes to you, but blue light does, meaning the sky appears blue to our eyes. Bingo! Since there is some green and other colors mixed in as well, the apparent color of the sky is more a blue-white than a pure blue.

(The Sun’s light doesn’t contain as much violet light as it does blue or red, so we won’t see a purple sky. It also helps that our eyes don’t respond strongly to violet light. The cone cells in our retinas are tuned to respond to blue, green, and red, so the other colors are perceived by triggering combinations of the primary cone cells.)

At sunset, light is traveling through a lot more air than it does at noon. That means every ray of light has more of a chance to scatter, removing the blue light before it reaches our eyes. What’s left is red light, making the sky at the horizon near the Sun appear red. In fact, you see more gradations of color too: moving your vision higher in the sky, you’ll note red shades into orange into yellow and so forth, but each color is less intense.

So finally: why is the Martian sky pink? The answer is dust: the surface of Mars is covered in a fine powder, more like talcum than sand. During the frequent windstorms that sweep across the planet, this dust is blown high into the air, where light (yes) scatters off of it. Since the grains are larger than air molecules, the kind of scattering is different, and tends to make the light appear red. (Actually, the sky’s “true” color is very hard to determine, since there is a lot more variation than on Earth.) When there is less dust in the atmosphere, the Martian sky is a deep blue, when the Sun’s light scatters off the carbon dioxide molecules in the air.

By DXS Physics Editor Matthew Francis

Double Xplainer: Once in a Blue Moon

Full Moon, from Flickr user Proggie under
Creative Commons license.
Tonight—August 31, 2012— is the second full Moon of August. The last time two full Moons occurred in the same month was in 2010, and the next will be in 2015, so while the events are rare, they aren’t terribly uncommon either. In fact, you’ve probably heard the second full Moon given a name: “blue moon”. (The Moon will not appear to be a blue color, though, cool as that would be. More on that in a bit.) What you may not know is that this term dates back only to 1946, and is actually a mistake.

According to Sky and Telescope, a premiere astronomy magazine (check your local library!), the writer James Hugh Pruett made an incorrect assumption about the use of the term “blue moon” in his March 1946 article. His source was the Maine Farmers’ Almanac, but he misinterpreted it. The almanac used “blue moon” to refer to the rare occasion when four full Moons happen in one season, when there are usually only three. By the almanac’s standards, tonight’s full moon is not a blue moon (though there will be one on August 21, 2013).

However, even that definition of “blue moon” apparently only dates to the early 19th century. In its colloquial, non-astronomical sense, a “blue moon” is something that rarely or never happens: like the Moon appearing blue. The Moon is white and gray when it’s high in the sky, and can appear very red, orange, or yellow near the horizon for the same reason the Sun does. As far as I can tell, the only time the Moon appears blue is when there’s a lot of volcanic ash in the air, also a rare event (thankfully) for most of the world. The popular song “Blue Moon” (written by everyone’s favorite gay misanthrope, Lorenz Hart) uses “blue” to mean sad, rather than rare.

I’m perfectly happy to keep the common mistaken usage of “blue moon” around, though, since it’s not really a big deal to me. Call tonight’s full Moon a blue moon, and I’ll back you up. However, because it’s me, let’s talk about the Moon and the Sun and why this stuff is kind of arbitrary.

The Moon and the Sun Don’t Get Along

The calendar used in much of the world is the Gregorian calendar, named for Pope Gregory XIII, who instituted it in 1582. The Gregorian calendar, in turn, was based on the older Roman calendar (known as the Julian calendar, for famous pinup girl Julie Callender Julius Caesar). The Romans’ calendar was based on the Sun: a year is the length of time for the Sun to return to the same spot in the sky. This length of time is approximate 365.25 days, which is why there’s a leap year every four years. (Experts know I’m simplifying; if you want more information, see this post at Galileo’s Pendulum.)

A problem arises when you try to break the year into smaller pieces. Traditionally, this has been done through reference to the Moon’s phases. The time to cycle through all the phases of the Moon is called a lunation, which is about 29 days, 12 hours, 44 minutes, and 3 seconds long. You don’t need to pull out a calculator to realize that a lunation doesn’t divide into a year evenly, but it’s still a reasonable way to mark the passage of time within a year, so it’s the foundation of the month (or moonth).

Many calendars—the traditional Chinese calendar, the Jewish calendar, and others—define the month based on a lunation, but don’t fix the number of months in a year. That means some years have 12 months, and others have 13: a leap month. It also means that holidays in these calendars move relative to the Gregorian calendar, such that Yom Kippur or the Chinese New Year don’t fall on the same date in 2012 that they did in 2011. (The Christian religious calendar combines aspects of the Jewish and the Gregorian calendars: Christmas is always December 25, but Easter and associated holidays are tied to Passover—which is coupled to the first full Moon after the spring equinox, and so can occur in a variety of dates in March and April.)

Another resolution to the problem of lunations vs. Sun is to ignore the Sun; this is what the Islamic calendar does. Months are defined by lunations, and the year is precisely 12 months, meaning the year in this calendar is 354 or 355 days long. This is why the holy month of Ramadan moves throughout the Gregorian year, happening sometimes in summer, and sometimes in winter.

The Gregorian calendar does things oppositely to the Islamic calendar: while months are defined, they are not based on a lunation at all. Months may be 30 days long (roughly one lunation), 31 days, or 28 days; the latter two options make no astronomical sense at all. Solar-only calendars have some advantages: since seasons are defined relative to the Sun, the equinoxes and solstices happen roughly on the same date every year, which doesn’t happen in lunation-based calendars. It’s all a matter of taste, culture, and convenience, however, since the cycles of Sun and the Moon don’t cooperate with the length of the day on Earth, or with each other.

Blue moons in the common post-1946 usage never happen in lunation-based calendar systems because by definition each phase of the Moon only occurs once in a month. On the other hand, the version from the Maine Farmers’ Almanac is relevant to any calendar system, because it’s defined by the seasons. As I wrote in my earlier DXS post, seasons are defined by the orbit of Earth around the Sun, and the relative orientation of Earth’s axis. Thus, summer is the same number of days whatever calendar system you use, even though it may not always be the same number of months. In a typical season, there will be three full Moons, but because of the mismatch between lunations and the time between equinoxes and solstices, some rare seasons may have four full Moons.

The Moon and Sun have provided patterns for human life and culture, metaphors for poetry and drama, and of course lots of superstition and pseudoscience. However, one thing most people can agree upon: the full Moon, blue or not, is a thing of beauty. If you can, go out tonight and have a look at it—and give it a wink in honor of the first human to set foot on it, Neil Armstrong.

Why blueberries won’t turn you blue and other blueberry facts

Blueberries. Credit.


by Adrienne Roehrich, Chemistry Editor

Blueberries in the Northwestern semisphere are the fruit of several shrubs in the genus Vaccinium L.  They grow in all provinces in Canada and all but two of the United States (Nebraska and North Dakota). In the Northwestern semisphere, one can find 43 species of blueberries, depending on the region. Blueberries are found and produced in all hemispheres of the world. However, the species can vary by region.

Taxonomy:
Kingdom: Plantae (Plants)
Subkingdom: Tracheobionta (Vascular plants)
Subdivision: Spermatophyta (Seed plants)
Division: Magnoliophyta (Flowering plants)
Class: Magnoliopsida (Dictyledons)
Subclass: Dilleniidae
Order: Ericales
Family: Ericaceae
Genus: Vaccinium

There are 43 species and 46 accepted taxa overall. Some of the species include fruits we do not necessarily recognize as blueberry, including farkleberry, bilberry, ohelo, cranberry, huckleberry, whortleberry, deer berry, and lingonberry.  (Source

Blueberries are a very popular fruit in the U.S., and is consumed in fresh, frozen, and canned forms. While blueberries are a great fruit to eat to meet your suggested fruit intake, it also is one of the foods that are purported to have properties that it just does not have. This undeserved reputation results from the high levels of anti-oxidants, leading those predisposed to looking for “super foods” to classify blueberries into the anti-oxidant super food category. While eating more healthy foods is always a good idea, no food has curative effects all on its own.

Other aspects of blueberry nutrition includes it as a source of sugar. One cup (148 g) of blueberries contains about 15 g of sugar and 4 g of fiber, a single gram of protein, and half a gram of fat. If you are counting carbs, this cup has 21 g of them. That one cup of blueberries averages about 85 calories, which is approximately the same as a medium apple or orange. While almost all the vitamins and minerals nutrition gurus like to report on are present to some amount, for the 2000-calorie diet, that one cup of blueberries will provide the recommended daily value of 24% of Vitamin C, 36% of Vitamin K, and 25% of manganese. The remaining values range from 0-4%. (Values obtained from Nutrition.com and verified through multiple sources.)

The Wikipedia entry is quite good and well researched (as of August 18, 2012). 

The photo above shows all of the life stages of a blueberry. Berries go from the little red nub at the end of the branch to round and juicy blueberries through fertilization of the ovary, which swells rapidly for about a month, then its growth ceases. The green berry develops with no change in size. The chemicals responsible for the blue color, anthocyanins, begin to turn the berry from green to blue as it develops over about 6 days. The volume of the berry increases during the change in color phase.

Will blueberries turn you blue? In short, no. You can achieve blue skin through the ill-advised practice of drinking silver or you can achieve orangish-yellow skin by eating a large number of carrots. This is because the chemicals causing the skin color are fat soluble and are present in a large quantity in the fat just under the skin, giving the skin those colors. Anthocyanin, the primary chemical causing the blue color in blueberries, is not fat soluble and will not reside in the fat under your skin.

Anthocyanins is a class of over 30 compounds. The chemical structure is generally as shown below. They are polyphenolic, which indicates the 3 ring structures. The “R” indicates different functional groups that change depending on which anthocyanin the structure represents. 


Interestingly, anthocyanins are also pH indicators because their color ranges from yellow to red to blue depending on the local pH. The blue color indicates a neutral pH. The wikipedia page on anthocyanins is also informative (as of August 18, 2012). 

As mentioned before, blueberries are a popular fruit. Recipes abound, but here is one from my own Recipe Codex for Surprise Muffins with blueberries:

Ingredients
  • 6 Tbsp. butter
  • 3/4 cup sugar
  • 2 eggs
  • 1/2 cup milk
  • 1/2 – 1 pint blueberries, fresh or frozen (defrosted)
  • Food coloring, optional
  • 2 cups all-purpose flour
  • 1/4 tsp. salt
  • 1 Tbsp. baking powder
  • Your favorite mini-treat (Hershey’s Kisses, Hugs, Reese’s Mini Cups, strawberry jam, etc.)
Directions
  1. Preheat the oven to 350º. In a large bowl, cream the butter and sugar. You can use a wooden spoon, a potato masher or handheld electric mixer. Mix in the eggs, one at a time, and add the milk.
  2. Rinse the strawberries and cut off the green stem. Mash the berries with a potato masher or puree in a blender. Then stir the berries into the butter and milk mixture. TIP: For muffins with a more blue color, add a few drops of blue food coloring.
  3. In a separate bowl, sift the flour, salt and baking powder. Stir well. Add the flour mixture to the berry mixture. Use a wooden spoon to stir until all the white disappears.
  4. Line the muffin tin with paper liners. Drop the batter from a tablespoon to fill the cups halfway.
  5. Add a surprise: an unwrapped mini treat or 1/2 teaspoon of jam. Then spoon more batter to fill almost to the top.
  6. Bake until the muffins begin to brown and a toothpick inserted near the center (but not in the mini-treat) comes out clean, about 20-25 minutes.
  7. Remove the muffins from the tin and cool.
Or perhaps you are in less of a cooking scientist mood and more in a home lab mood. Try this at-home lab with blueberries about dyes. Adapted from the Journal of Chemical Education.

Items You Need
  • 4 microwavable/stove top staff glasses, pots, or containers at least 1/2 cup in volume
  • tablespoons or 1/4 cup measuring cup
  • water
  • spatula
  • alum (available in the grocery store spice aisle)
  • cream of tartar (available in the grocery store spice aisle)
  • hot pads and tongs
  • at least four small (1-2 in.) squares of white cotton cloth
  • yellow onion skins
  • blueberries
  • spoon
  • paper towels
  • vinegar
  • baking soda
  • a dropper
  • notebook for experimental observations
Procedure
In each step, you will want to record your observations, paying special attention to colors.
  1. Pour 4 tablespoons (1/4 cup) into container 1. Add a pea-sized scoop of alum and about half that amount of cream of tartar and stir. Bring the solution to a boil on the stove top or by microwaving for about 60 seconds. (Your microwave may vary.) Add two small squares of white cotton cloth and boil for two minutes. Set the container aside. The squares will be used in steps 4 and 6.
  2. Tear the outer, papery skin from a yellow onion into pieces no more than 1 inch square. Place enough pieces in a second container to cover its bottom with  2 or 3 layers of onion skin. Add about 4 tablespoons of water to the container. Bring the solution to a boil on the stove top, continuing to boil for 5  minutes.
  3. Wet a new square of cloth with water. Place it in container 2 so it is completely submerged and boil for 1 minute. Using tongs, remove the cloth and rinse it with water. Place the cloth square in the appropriate area on a labeled paper towel.
  4. Use tongs to remove one of the cloth squares from beaker 1. Repeat step 3 using this square. Compare to the dyed cloth square from step 3.
  5. Pour 4 tablespoons of water in a third container. Add 4-5 blueberries to the container and mash them with a spoon. Bring the solution to a boil on the stove, and continue to boil for 5 minutes.
  6. Repeat steps 3 and 4 substituting the blueberry mixture in container 3 for the onion skin mixture in container 2.
  7. Mix a small scoop of baking soda with a tsp of water in a clean container. With a dropper, place 1-2 drops of the baking soda solution in one corner of each cloth square. What happens? Rinse the dropper thoroughly, then place 1-2 drops of vinegar on the opposite corner of each square. What happens? Rinse the fabric squares under cool running water. Is there a change? Allow the squares to dry overnight. Is there any change of the cloth dries?
Optional: Try variations in the procedure such as changing the amount of dye source, the length of time the cloth spends in the dye solution, and the temperature of the dye solution.

Questions to consider
The solution in step 1 is called a mordant. Based on your observations, what is the purpose of a mordant?
Is the dye produced by blueberries really blue? Why might some people not want to wear clothes dyed with blueberries?

———————-
All in all, enjoy your blueberries. As a shrub, it is quite pretty. As a fruit, it is quite yummy. And as the tool in an experiment, it is quite fun.

These views are the opinion of the author and do not necessarily reflect or disagree with those of the DXS editorial team.

Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

The short version
  • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
  • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
  • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
  • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
The longer version
Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.

                                                  

Big Molecules with Small Building Blocks

The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.
Carbohydrates

You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

Sugar and Fuel

A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

Polysaccharides: Fuel and Form

Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

Lipids: The Fatty Trifecta

Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

Fats: the Good, the Bad, the Neutral

Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

Phospholipids: An Abundant Fat

You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

Steroids: Here to Pump You Up?

Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.

Proteins

As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

Levels of Structure

Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

A Plethora of Purposes

What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

Nucleic Acids

How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

DNA vs. RNA: A Matter of Structure

DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

DNA vs. RNA: Function Wars

An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.


 By Emily Willingham, DXS managing editor 
This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

Aren’t you curious?


Source: IFLS
By Courtney Williams, DXS contributor
Recently my on-line science pal Emily J. Willingham asked on Facebook,
“You are a consumer of science. As one, what bothers you about how science is offered to you? What questions do you have? How do you consume scientific information? How do you use it?”
She’s going to be blogging on the Forbes network, see her here, and I’m guessing this was the impetus for that particular set of questions.I had much to say in answer to her questions.
One of my biggest pet peeves is that the most sensational headlines are used- even if they are entirely inaccurate scientifically. For example the recent news about small pox and breast cancer. Headlines like, “New smallpox virus could ‘cure’ breast cancer, studies reveal.” How many ways is that wrong?  Well, it’s not smallpox the researchers were using, it’s a vaccinia virus, which is in the same family as the smallpox virus. Big difference. For instance, there wasn’t a global effort to eradicate cowpox- another vaccinia family member. Just because the viruses are related doesn’t mean they are the same thing. Also, what’s with the quotation marks around cure?Maybe because it’s not actually a cure, not even a treatment, just an interesting experiment done in mice- but cure (even in quotes) makes for a better headline. [If you want to learn about the real science behind that crappy headline, here's the original paper- "Vaccinia Virus GLV-1h153 Is Effective in Treating and Preventing Metastatic Triple-Negative Breast Cancer"]
Articles rarely cite their scientific sources- i.e. linking to the actual journal article they are writing about. For instance, the craptastic example above where the ‘journalist’ (how’s that for quotation marks?) not only failed to link to the original article, he didn’t even mention the journal it was published in, when it was published, or any other info (other than the lead author’s name) that would help a reader find the journal article or additional info on it.
As for sources, it’s important to distinguish for the reader between peer reviewed journal articles and mere opinion pieces on blogs. Take for instance the blog post I wrote about here that appeared on the website of Psychology Today. Many news outlets picked it up and touted it as research that showed it was dangerous to let your infant ‘cry it out’ when really it was just a post (poorly researched, lacking citations, and full of unsupported conjecture and opinion) on the blog of a psychologist. A blog post is NOT the same thing as a peer reviewed journal article. Please journalists, know this!
Another gripe, accuracy is sacrificed for the sake of brevity, which completely defeats the purpose of sharing the science. See above yet again about smallpox as a ‘cure’ for breast cancer.
Another problem I have is the way the media handles funding sources for research studies- they always matter, it’s imperative that scientists report any conflicts of interest that funding sources might prove to be. However, they are not always a sign that researchers are ‘in cahoots’ with the companies that fund them. For instance, would you trust RJ Reynolds to fund unbiased research on smoking and cancer? Probably not. Thus, if at the end of a research article you see a company with a known bias and the findings support their assertions, you are right to be skeptical. However, sometimes the funding merely means a company paid for work to be done, regardless of the outcome. For instance, a pharma company that partners with an academic lab on basic science and published the results in a peer reviewed journal. Or, a drug company that funds the clinical trials for it’s drugs. That’s just the way it works- who else would fund the trial if not the manufacturer? If those types of studies are published in peer reviewed journals, they have been vetted to that extent. Further, with clinical trials, the Federal Drug Administration (FDA) oversees all those trials to help ensure they are unbiased and protect the patients involved as well as the public as a whole. The media seems unable to distinguish.
As for how I generally consume science/scientific information? It’s usually as follows- hear about it on the radio or read a lame article via Yahoo News/Strollerderby/The Stir/etc., assume the author is either full of bologna, got the science partly/mostly wrong, had their more level-headed title replaced by an editor, is totally biased, etc., then I track down the original research article, and possibly seek out commentaries on the work from reliable sources (SciAm blogsDouble X Science, fellow scientists, etc.).
What about how I use it? Well, obviously I’m a scientist, so I ‘use’ science/scientific information professionally every single (work) day to try and cure (no quotation marks) and/or treat cancer. In my personal life, science helps me make healthcare decisions for myself and my family, decide which products to buy or to avoid, answer questions about the natural world when my toddler asks, as  material to blog about and use to dispel misconceptions held by myself and others.
However, a lot of the time I don’t necessarily even use the science I consume. Sometimes I just want to know it. I’m curious.
Pretty frequently people ask me, “How do you know that?” or “Why do you even know that?” I’m not sure how to answer. If it’s a medical question, a lot of the times the answer is, “Well, I have that body part and I want to know how it works.” Or, “Well, I’m taking that medicine, so I looked up how it works.” People forget that science is the basis of everything- it’s how everything works or came to be.  While others seem to find it odd that I’m always looking up the science behind was I see/do/hear about, I find it odd that other don’t seem to question enough.
You’re taking that medicine, you’re having that surgery, you’re using that product right now- don’t you wonder how/why it works? Why aren’t you wondering?
Where’s your curiosity? Don’t you just want to know why the sky is blue? How did you came to be? Why are roses red and violets blue?
Aren’t you curious?
The opinions in this article do not necessarily reflect or conflict with those of the DXS editorial team and its contributors.———————————————
Courtney Williams is a scientist, wife, and mother (in no particular order). She works in the oncology department of a biotech company in the burbs of NYC. She blogs about marriage, motherhood, and science at http://mommacommaphd.wordpress.com/.

To Everything (Turn Turn Turn) There is a Season

Today – June 20 – is the northern Summer Solstice, sometimes known as the Northern Solstice, “first day of summer”, or Midsummer’s Day, depending on where you live. It’s the longest day and shortest night of the year in the northern hemisphere (where I live), though exactly howlong or short depends on how far north you live. And of course in the southern hemisphere, today is is the shortest day and longest night, since the seasons are reversed.
The secret to the solstice and to Earth’s seasons in general involves the tilt of Earth’s axis. Our planet orbits the Sun in an elliptical path, which you can draw on a flat piece of paper: it doesn’t move “up” or “down”, but stays in a single plane known as the ecliptic. (The name “ecliptic”, as you might guess, is related to the word “eclipse”, since ancient astronomers determined eclipses of the Moon and Sun could only occur at certain places in the sky.) Earth’s axis is tilted compared to the ecliptic, and the axis points more or less in the same direction, wherever the planet is in its orbit. The axis points almost directly at Polaris, the North Star, which is why that star is a good navigational guide for those in the northern hemisphere: no matter what time of year, it’s always in the same spot in the sky. Other stars rise and set as Earth rotates, but not Polaris. (Unfortunately, there isn’t a South Star.)
As you can see from the diagram above, during about half the year, the North Pole points more toward the Sun, while it points more away for the rest of the year. Where I live, the Sun will never be directly overhead, even at noon. The farthest north that will ever happen is a special latitude known as the Tropic of Cancer – and the northern Summer Solstice is the day that occurs. On the northern Winter Solstice, which happens on December 21 or 22, the Sun is directly overhead at noon at the latitude of the Tropic of Capricorn.
Now we can see why summers are hot! In summer, the Sun rises earlier, sets later, and reaches a higher point in the sky. Those things combined mean extra sunlight, heating up the air and the ground longer. We can also see why I put “first day of summer” in quotes: the Solstice is the apex of the process, but the increase in daylight and temperatures begins long before June 20 (at least every place I’ve lived). The Midsummer’s Day festival, celebrated throughout northern Europe, acknowledges that; Shakespeare’s play A Midsummer Night’s Dream may have been written for the English version of the festival (though from what I can tell, the historical evidence is scant).
Similarly, during winter the Sun’s light comes in at a steeper angle and days are shorter, so the time for the ground to warm is greatly reduced. The northern Winter Solstice (also known as the Southern Solstice, “first day of winter”, Midwinter’s Day, or Yule) is the shortest day and longest night of the year in the northern hemisphere. On that day, the North Pole points as far away from the Sun as it ever does. We also have the reason the tropics are warm all year around: they receive about the same amount of sunlight during both summer and winter.
Approximately halfway between the solstices, the Sun appears directly overhead at noon at the Equator. On those days, everywhere on Earth gets about 12 hours of daylight and 12 hours of night. These days are the equinoxes, meaning “equal night”. (The spell to extinguish light in the Harry Potter books is “nox”, for what it’s worth. Yes, I remember such things. I’m still waiting for my “accio!” summoning spell, though.) The two days are known as the Vernal(or spring) and the Autumnal (or autumn) Equinox, again based on the seasons in the northern hemisphere. From an astronomical point of view, Earth’s “solar year” is marked between successive vernal equinoxes. (A second measurement of the year, known as the sidereal year, is measured with respect to the stars. These two year measurements are almost, but not quite, the same length!)
Now let’s put all of this together in a movie! (For some reason, the Sun – which was a gently glowing lamp in my original simulation – came out looking flat and boring in the final movie. I guess I still have more to learn about creating three-dimensional animations.) For best results, please view this full-screen.

You – Yes, You – Are an Astronomer

On January 7, 1610 (402 years ago today!), Galileo first identified three moons of Jupiter, the first satellites ever observed orbiting another planet. He later found a fourth, and today those moons — Io, Europa, Ganymede, and Callisto — are known as the Galilean moons in his honor. Galileo was able to do this because he used a telescope to observe: every new way to see reveals something new to be seen.

You can buy a telescope that’s more or less equivalent to Galileo’s ‘scope here for a very low price. (It’s actually much better, in my opinion, since the housing is made of plastic instead of cardboard! Also, you don’t have to grind your own lenses.) I don’t endorse most products, but I’ll happily plug this one: it’s a non-profit group whose aim is to get people looking at the skies, and I’ve used these ‘scopes in my astronomy classes. What was a specialist’s tool in 1610 is something available for everyone today; you can even see the four Galilean moons of Jupiter with a decent pair of binoculars.

I spent the holidays with my family in Iowa: my parents live in a very very very small town, without much light pollution. It was clear at night several days, and so we went out in the backyard to see what we could see. With my parents’ binoculars, we managed to see all four Galilean moons, and over three nights of viewing, saw how their positions changed as they orbit Jupiter. We were doing astronomy in the backyard: no specialized equipment, no special training, no observatory needed. Even in a city, you can still see the brighter planets (Jupiter is the third-brightest object in the night sky, after the Moon and Venus), and if your city is like mine, amateur astronomy groups are around that set up public nights to show you the sights.

You don’t need to be a trained professional to be an astronomer. You don’t need a huge telescope. You just need to look up. You can learn to read the night sky, identify planets, look for interesting nebulae and stars. If the sky is clear tonight, you can go outside and see Jupiter after sundown, and if you have binoculars or a small telescope, all four Galilean moons will even be visible. Jupiter is high above the horizon, and the brightest object other than the Moon tonight. Go look, and when you’re done, call yourself an astronomer. I’ll back you up.

(This post originally appeared at Galileo’s Pendulum.)